A magnetic disk drive generally includes a magnetic disk (recording medium) and at least one magnetic head(s) positioned to face the magnetic disk. As the magnetic disk is rotated at a high speed, the magnetic head is driven in a radial direction of the magnetic disk using a driving unit so that data is recorded at predetermined positions on the magnetic disk.
As shown in FIG. 11(A), a plurality of concentric tracks 3 for registering data are formed around a shaft 2 for a magnetic disk 1 (in FIG. 11(A), only one track 3 is shown). As shown in FIG. 11(B), a stack of magnetic disks 1 is normally provided on the shaft 2 (FIG. 11(A)). Two magnetic heads (not shown) positioned opposite to each other sandwich each magnetic disk 1 (FIG. 11(B)).
The plurality of magnetic heads are moved together by driving means such as a voice coil motor (VCM). Corresponding tracks 3 on the disks 1 form a cylinder 4. Each of the tracks 3 (FIG. 11(A)) is divided into a plurality of sectors 7. Each of the sectors 7 has a servo area 5 (servo sector) in which servo information necessary for the seek operation is recorded, and a data area 6 (data sector) in which data is recorded by a user of the magnetic disk drive.
FIG. 10 shows a format of servo information recorded on a conventional servo sector 5. The servo information recorded in the servo sector 5 is used for radial positioning of a magnetic head to a desired track or cylinder, and for detecting circumferential positions of the magnetic head within the selected track. As shown in FIG. 10, servo information recorded in one servo sector includes address information 59 including a servo mark 51 (SM), cylinder information 52 (CYL), and head information 53. The servo information also includes position information 54 (POSITION).
The servo mark 51 is provided to distinguish the servo sector 5 from the previous data sector 6. The cylinder information 52 specifies a cylinder address. Specifically, gray codes are used to record the cylinder information 52 in order to prevent an erroneous reading of cylinder information from occurring.
The head information 53 is embodied by an identification number for a head used to process the track. Therefore, the head information 53 remains the same for a given track. The position information 54 includes servo A 55, servo B 56, servo C 57, and servo D 58, and is used to generate signals indicating positions between tracks.
Though not illustrated, the data sector 6 includes an ID field and a data field. The data field is used as a data area in which data is recorded by the user of the magnetic disk. A portion of the servo information including the cylinder information and the head information is recorded in the ID field.
Conventionally, the full cylinder information is recorded in the ID field of the data sector 6, and only a low-order portion of the cylinder information is recorded in the area in the servo sector 5 reserved for the cylinder information (CYL). Therefore, in the conventional magnetic disk drive, the position of the magnetic head is determined before the read/write operation based on the cylinder information recorded in the ID field of the data sector 6.
The ID field in the data sector 6 makes it possible to obtain cylinder information even when the magnetic head is not aligned with the center of recorded data. Recently, however, the ID field tends to be eliminated from the data sector 6 in the magnetic drive in order to provide more efficient data recording, that is, for improved density of data recording. In this case, the position of the magnetic head is determined before the read/write operation based on the servo information recorded in the servo sector 5.
In an approach in which the position is determined before the read/write operation using the servo information, it is necessary to record the full-bit servo information in the area in the servo sector 5 reserved for the cylinder information (CYL).
As the track pitch becomes smaller due to increased recording density, the number of tracks formed on the magnetic disk 1 increases and the number of cylinders increases. Accordingly, it is necessary to expand the area reserved for the cylinder information (CYL). Specifically, given 3,000 cylinders in the conventional magnetic disk, the capacity of the area reserved for the cylinder information (CYL) is 12 bits. As the number of cylinders increases to 10,000 as a result of improved recording density, the capacity of 14 bits is required for the cylinder information.
As the number of cylinders increases, the volume of cylinder information increases. In an approach in which the full-bit cylinder information is recorded in each of the servo sectors 5, the area reserved for cylinder information grows significantly, resulting in a reduction in the size of the area available for recording data, and a consequent reduction in recording efficiency.
Accordingly, an object of the present invention is to provide an information recording medium and an information recording device in which recording efficiency is improved.